Kinetics on thermal soaking of mesophase pitch at processing temperature and its influence on the derived carbon structure

Mesophase pitch (MP) is an attractive precursor for tailoring high-performance carbon fibers due to its aromatic hydrocarbons mesogenic components that self-assemble into highly ordered microstructures. Relating processing conditions to the evolution of MP microstructure and its inheritance in carbon materials remains a challenge. This work quantitatively determined the kinetics of mesogenic aggregation in MP at spinning temperatures for the first time. Polarized optical microscopy tracked domain size changes in MP during 1–24 h thermal soaking. Analysis using an exponential growth model revealed nonlinear growth kinetics with an activation energy of just 39.3 kJ·mol−1, suggesting mesogenic aggregation is facile at processing temperatures compared to mesophase formation. Prolonged thermal soaking promoted microcrystalline development in derived carbon fibers, evident from increased crystallite stacking and reduced interlayer spacing. Relating microstructural evolution in the MP to the resulting carbon fiber structure provides new insights to tailor carbon materials for applications. This work revealed the kinetics of MP at its processing temperature, provides a valuable insight into the future optimization of processing conditions for MP based carbon materials. •Domain size determination from polarized optical texture was used in assessment of kinetics data.•The kinetics of mesogenic aggregation in mesophase pitch at spinning temperatures were quantitatively determined.•The kinetics follows nonlinear growth model with an activation energy of only 39.3 kJ·mol−1.•Prolonged thermal soaking promotes microcrystalline development in derived carbon fibers.